In physical vapor deposition (PVD) as well as in chemical vapor deposition (CVD) techniques, factors providing deposition of homogeneous phosphor or scintillator coating compositions and homogeneous layer thicknesses over the entire surface thereof, besides use of especially designed electrically heated crucible(s) are related with the distance determining the profile of the vapor cloud at the position of the substrate, as has e.g. been described in EP-Applications Nos. 03 100 723, filed Mar. 20, 2003 and 04 101 138, filed Mar. 19, 2004.
Average values of shortest distances between crucible(s) and substrate are preferably in the range of from 5 to 10 cm. Too large distances would lead to loss of material and decreased yield of the process, whereas too small distances would lead to too high a temperature of the substrate.
Care should however be taken in order to avoid “spot errors” or “pits”, resulting in uneven deposit of phosphors or scintillators, due to spitting of the liquefied raw materials present in the heated container(s): besides physical presence of an undesired unevenness at the surface, differences in speed or sensitivity may lay burden on its use as a screen, plate or panel for use in diagnostic imaging, especially when those phosphors are suitable for use in direct radiography as scintillators, in intensifying screens as prompt emitting phosphors or in storage panels as stimulable phosphors, used in computed radiography (CR).